1. Field of the Invention
The present invention generally relates to a planar lamp for illuminating a flat panel display. More particularly, the present invention relates to a planar light unit of field emitters whose cathodes and gates are arranged in strip shape for use in flat panel displays.
2. Background of the Invention
In recent years, flat panel display devices have been developed and widely used in electronic applications such as computer monitors and televisions. One of the popularly used flat panel display device is an active matrix liquid crystal display (LCD) that provides improved resolution. Other flat panel display devices have been developed in recent years to replace the liquid crystal display panels. One of such devices is a field emission display (FED) device that overcomes some of the limitations of LCD and provides significant advantages over the traditional LCD devices. For instance, the FED devices have higher contrast ratio, larger viewing angle, higher maximum brightness, lower power consumption and a wider operating temperature range when compared to a conventional thin film transistor (TFT) LCD panel.
A most drastic difference between a FED and a LCD is that, unlike the LCD, FED produces its own light source. In a FED, electrons are emitted from a cathode and impinge on phosphors coated on the back of a transparent cover plate to produce an image. Such a cathodoluminescent process is known as one of the most efficient methods for generating light. Contrary to a conventional CRT device, each pixel or emission unit in a FED has its own electron source, i.e., typically an array of emitting microtips. A voltage difference existed between a cathode and a gate which extracts electrons from the cathode and accelerates them toward the phosphor coating. The emission current, and thus the display brightness, is strongly dependent on the work function of the material formed on the emitting microtips.
Referring to FIG. 1A, a top view of a conventional field emission display device 1 using carbon nanotube (CNT) emitters as electron emission sources is shown. FIG. 1B is a partial, cross-sectional view of the conventional field emission display device 1 taken along a line A-A of FIG. 1A. As shown in FIGS. 1A and 1B, the FED device 1 is constructed by a first insulative plate 10, cathode electrodes 12 formed on the first insulative plate 10 by a material that includes metal, CNT emitters 16 formed on the cathode electrodes 12 to form emitter stacks 17, dielectric strips 18 formed on the insulating plate 10 and perpendicular to a multiplicity of the emitter stacks 17, gate electrodes 14 formed on top of the dielectric strips 18, and anode electrodes 15 coated with phosphorous particles formed on a second insulative plate 11 mounted on top of the first insulative plate 10, and an intermittent conductive layer of indium-tin-oxide (ITO) layer 13 formed between the second insulative plate 11 and the anode electrodes 15 to further improve the brightness of the phosphorous layer of the anode electrodes 15 when bombarded by electrons.
It is therefore an object of the present invention to provide a planar light unit utilizes field emitters which higher maximum brightness, lower power consumption and a wider operating temperature range.